The present invention relates to a cationic polymer flocculant having excellent stability.
Formerly, the present inventors have found that a polymer substance having quarternary ammonium groups obtained by polycondensation of epihalohydrin and Mannich reaction products of monohydric phenol, that is, the amines mainly comprising phenol derivatives having dialkylaminomethyl groups which have been introduced to the monohydric phenol by reacting dialkylamine and formaldehyde with the eiphalohydrin has an excellent flocculation capability, and then have proposed a cationic polymer flocculant comprising the thus obtained polycondensate (refer to Japanese Patent Application Laying Open No. 35185/79 which corresponds to U.S. Pat. No. 4,155,847).
However, there is a tendency of molecular weight-reduction in the above-mentioned polycondensate due to the occurrence of break down of the main chain with the progress of time. Consequently, the amount of polymeric cation determined by colloid titration showed a gradual reduction resulting in a tendency of the reduction of performance as a polymer flocculant.
For instance, the polycondensate of epichlorohydrin and Mannich reaction products obtained by reacting three moles of formaldehyde and three moles of dimethylamine with one mole of phenol showed a conspicuous break down of the polymer molecule particularly in an aqueous solution at a high temperature and at a low concentration. For instance, after keeping 0.5% aqueous solution of the above-mentioned polycondensate at 50.degree. C. for one day, the amount of polymeric cations became 38% by mole of the original amount.
Although trials have been carried out to quarternize a part of the dialkylaminomethyl groups with lower alkyl halide in order to prevent the deterioration of the polycondensate, there is no advantage in this method of complicating the reaction steps.